…witched to

After a turn checked out another branch, its diff compared against the previous
checkpoint, so the left branch's work showed as deletions and edits to shared
files showed the old branch's content as the removed side.

Each checkpoint now records where HEAD's reflog ended. The next capture reads
only the entries after that cursor, and for each `checkout: moving from` entry
takes the files the switch changed from the branch it landed on. That baseline
becomes the checkpoint's second parent, and the adjacent turn diff starts there.
Resets, rebases, merges and branch renames are not checkouts, so their changes
stay in the diff. A rewritten or missing reflog leaves no baseline.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

…on-UTF-8 file names

Co-Authored-By: Claude Opus 5.5 <[email protected]>

# Conflicts:
#	apps/server/src/checkpointing/CheckpointStore.test.ts

… rev-parse

Capture already resolves its repository paths in one rev-parse; ask it for
logs/HEAD too so branch-switch tracking does not add a second call.

AI-assisted; verified with the tests and tools listed above.

…arried

Replaying a switch replaced every changed path with the destination blob,
so local edits that git switch -m merged forward showed up again as the
new turn's work. Paths the baseline had edited relative to the switch's
source commit now keep the baseline's content.

AI-assisted; verified with the tests and tools listed above.

The carried-edit filter compared the baseline with each switch's source
commit, so a commit between two switches made the switch back look like
a local edit and left branch content in the baseline. It now uses the
previous checkpoint's own edits over its HEAD, computed once. Gitlinks
are left out of the replay because a plain switch does not move a
submodule.

AI-assisted; verified with the tests and tools listed above.